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Posted to issues@spark.apache.org by "Liang-Chi Hsieh (JIRA)" <ji...@apache.org> on 2018/01/26 02:51:00 UTC
[jira] [Commented] (SPARK-23220) broadcast hint not applied in a
streaming left anti join
[ https://issues.apache.org/jira/browse/SPARK-23220?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16340495#comment-16340495 ]
Liang-Chi Hsieh commented on SPARK-23220:
-----------------------------------------
I can't re-produce it locally. I join a stream with a static dataframe similarly, but the broadcast hint does work as expected. Can you provide a small reproducible example? Thanks.
> broadcast hint not applied in a streaming left anti join
> --------------------------------------------------------
>
> Key: SPARK-23220
> URL: https://issues.apache.org/jira/browse/SPARK-23220
> Project: Spark
> Issue Type: Bug
> Components: Structured Streaming
> Affects Versions: 2.2.1
> Reporter: Mathieu DESPRIEE
> Priority: Major
> Attachments: Screenshot from 2018-01-25 17-32-45.png
>
>
> We have a structured streaming app doing a left anti-join between a stream, and a static dataframe. This one is quite small (a few 100s of rows), but the query plan by default is a sort merge join.
>
> It happens sometimes we need to re-process some historical data, so we feed the same app with a FileSource pointing to our S3 storage with all archives. In that situation, the first mini-batch is quite heavy (several 100'000s of input files), and the time spent in sort-merge join is non-acceptable. Additionally it's highly skewed, so partition sizes are completely uneven, and executors tend to crash with OOMs.
> I tried to switch to a broadcast join, but Spark still applies a sort-merge.
> {noformat}
> ds.join(broadcast(hostnames), Seq("hostname"), "leftanti")
> {noformat}
> !Screenshot from 2018-01-25 17-32-45.png!
> The logical plan is :
> {noformat}
> Project [app_id#5203, <--- snip ---> ... 18 more fields]
> +- Project ...
> <-- snip -->
> +- Join LeftAnti, (hostname#3584 = hostname#190)
> :- Project [app_id, ...
> <-- snip -->
> +- StreamingExecutionRelation FileStreamSource[s3://xxxx{/2018/{01,02}/*/*/,/2017/{08,09,10,11,12}/*/*/}], [app_id
> <--snip--> ... 62 more fields]
> +- ResolvedHint isBroadcastable=true
> +- Relation[hostname#190,descr#191] RedshiftRelation("PUBLIC"."hostname_filter")
> {noformat}
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